ci,test(ct): try to use an optional base image ref for app image push…

… flow

We need to transfer the determined base image name we might have just built from the calling workflow into this flow.

It's not yet clear how and if this works properly with pull requests.

.github/workflows/container_app_push.yml

@@ -6,10 +6,11 @@ on:
     # Instead, push events will trigger from the base image and maven unit tests via workflow_call.
     workflow_call:
         inputs:
-            branch:
+            base-image-ref:
                 type: string
-                description: "A tag or branch to checkout for building the image"
-                required: true
+                description: "Reference of the base image to build on in full qualified form [<registry>/]<namespace>/<repo>:<tag>"
+                required: false
+                default: "gdcc/base:unstable"
     pull_request:
         branches:
             - develop
@@ -21,7 +22,6 @@ on:
 
 env:
     IMAGE_TAG: unstable
-    BASE_IMAGE_TAG: unstable
     REGISTRY: "" # Empty means default to Docker Hub
     PLATFORMS: "linux/amd64,linux/arm64"
     MASTER_BRANCH_TAG: alpha
@@ -52,6 +52,7 @@ jobs:
               run: >
                   mvn -B -f modules/dataverse-parent
                   -P ct -pl edu.harvard.iq:dataverse -am
+                  -Dbase.image.tag=${{ inputs.base-image-ref }}
                   install
 
             # TODO: add smoke / integration testing here (add "-Pct -DskipIntegrationTests=false")